DESCRIPTION: Continued ultrastructural and functional studies of fiber cell junctions in normal aging and cataractous lenses are proposed. High resolution LM studies on vibratome sections of fresh lenses will be used to complement EM studies on similar preparations, permitting an excellent degree of correlation between the two. The principal aim is to use comparison of normal and cataractous lenses to define the causes of light scatter. The central hypothesis is that the breakdown of plasma membranes is followed by a leakage of cytoplasmic contents creating local refractive index variations at cell interfaces. Also evaluated will be a) cell viability in the nuclear core using confocal microcopy b) the preservation of membranes in the oldest cells by TEM, c) Fourier analysis of cytoplasmic texture d) the definition of protein-like deposits in the extracellular space. Also characterized will be light scatter centers in nuclei from human diabetic lenses, and spontaneously occurring diabetic canine lenses.